Catalysts

ABSTRACT

The invention describes ligands of formula (I), wherein LIG represents an η 5 -ligand substituted by a group R 1  and a group (R″) m ; X represents a 1 to 3 atom bridge; Y represents a nitrogen or phosphorus atom; Z represents a carbon, nitrogen or phosphorus atom.

This invention relates to catalysts for olefin polymerisation, inparticular to catalyst compounds containing metals η-bonded byη⁵-ligands, e.g. cyclopentadienyl ligands and η or σ-bonded by abicyclic nitrogen ligand, and their use in olefin polymerisation.

In olefin polymerization, it has long been known to use as a catalystsystem the combination of a metallocene procatalyst and an alumoxane orboron based co-catalyst.

By “metallocene” is here meant an η-ligand metal complex, e.g. an “opensandwich” or “half sandwich” compound in which the metal is complexed bya single η-ligand, a “sandwich” compound in which the metal is complexedby two or more η-ligands, a “handcuff” compound” in which the metal iscomplexed by a bridged bis-η-ligand or a “scorpionate” compound in whichthe metal is complexed by an η-ligand linked by a bridge to a σ-ligand.

Metallocene procatalysts are generally used as part of a catalyst systemwhich also includes an ionic cocatalyst or catalyst activator, forexample, an aluminoxane (e.g. methylaluminoxane (MAO),hexaisobutylaluminoxane and tetraisobutylaluminoxane) or a boroncompound (e.g. a fluoroboron compound such as triphenylpentafluoroboronor triphentylcarbenium tetraphenylpentafluoroborate ((C₆H₅)₃B⁺B⁻(C₆F₅)₄))

Alumoxanes are compounds with alternating aluminium and oxygen atomsgenerally compounds of formula

where each R, which may be the same or different, is a C₁₋₁₀ alkylgroup, and p is an integer having a value between 0 and 40). Thesecompounds may be prepared by reaction of an aluminium alkyl with water.The production and use of alumoxanes is described in the patentliterature, especially the patent applications of Texas Alkyls,Albemarle, Ethyl, Phillips, Akzo Nobel, Exxon, Idemitsu Kosan, Witco,BASF and Mitsui.

Traditionally, the most widely used alumoxane is methylalumoxane (MAO),an alumoxane compound in which the R groups are methyls. MAO however ispoorly characterised and relatively expensive and efforts have been madeto use alumoxanes other than MAO. Thus, for example WO98/32775(Borealis) proposes the use of metallocene procatalysts with alumoxanesin which R is a C₂₋₁₀ alkyl group, eg hexaisobutylalumoxane (HIBAO).However, such metallocenes generally have poor catalyst activities withnon-MAO alumoxanes.

Since each polymerisation catalyst gives rise to polymer products withslightly differing properties, there remains an ongoing search for newand improved olefin polymerisation catalysts.

We have now surprisingly found that a single site procatalyst systembased on a η⁵-ligand, e.g. cyclopentadienyl type ligand and a η orσ-bonding bicyclic nitrogen ligand may be used very effectively inpolymerisation catalysis, especially in the manufacture of polyethyleneor polypropylene.

Thus viewed from one aspect the invention provides a compound of formula(I) comprising

wherein

LIG represents an η⁵-ligand substituted by a group R₁ and a group(R″)_(m);

X represents a 1 to 3 atom bridge, optionally substituted, e.g. by R″groups;

Y represents a nitrogen or phosphorus atom;

Z represents a carbon, silicon, nitrogen or phosphorus atom;

the ring denoted by A₁ is an optionally substituted, optionallysaturated or unsaturated 5 to 12 membered heterocyclic ring;

the ring denoted by A₂ is an optionally substituted, unsaturated 5 to 12membered heterocyclic ring;

R₁ represents hydrogen, R″ or a group OSiR′₃;

each R′, which may be the same or different is a R⁺, OR⁺, SR⁺, NR⁺ ₂ orPR⁺ ₂ group where each R⁺ is a C₁₋₁₆ hydrocarbyl group, a tri-C₁₋₈hydrocarbylsilyl group or a tri-C₁₋₈hydrocarbylsiloxy group, preferablyR′ being a C₁₋₁₂ hydrocarbyl group, e.g. a C₁₋₈ alkyl or alkenyl group;

each R″, which may be the same or different is a ring substituent whichdoes not form a σ-bond to a metal η-bonded by the bicyclic ring, eg itmay be hydrogen, R⁺, OR⁺, SR⁺, NR⁺ ₂ or PR⁺ ₂ group where each R⁺ is aC₁₋₁₆ hydrocarbyl group, a tri-C₁₋₈ hydrocarbylsilyl group or atri-C₁₋₈hydrocarbylsiloxy group; and

m is zero or an integer between 1 and 3.

Viewed from a further aspect the invention provides an olefinpolymerisation catalyst system comprising or produced by reaction of (1)a metallated compound as hereinbefore defined (from hereon called aprocatalyst) and (2) a cocatalyst, e.g. an aluminium alkyl compound orboron compound, in particular an alumoxane, especially an aluminiumalkyl compound comprising alkyl groups containing at least two carbonatoms.

Viewed from a still further aspect the invention provides a process forolefin polymerisation comprising polymerising an olefin in the presenceof a catalyst system as hereinbefore described.

Viewed from a yet further aspect the invention provides a process forthe preparation of a procatalyst, said process comprising metallatingwith a group 3 to 7 transition metal a compound of formula (I)

wherein LIG, X, Y, Z and rings A₁ and A₂ are as hereinbefore defined.

Viewed from a further aspect the invention provides the use of aprocatalyst as hereinbefore defined in olefin polymerization, especiallyethylene or propylene polymerisation or copolymerisation.

Viewed from a yet further aspect the invention provides an olefinpolymer produced by a polymerisation catalysed by a procatalyst compoundas hereinbefore defined.

The compounds of formula (I) as hereinbefore described may be coupledwith a metal from groups 3 to 7. By group 3 (etc) metal is meant a metalin group 3 of the Periodic Table of the Elements, namely Sc, Y, etc. Itis preferable if the metal coupling the compound of the invention is inthe III⁺ oxidation state, although metals in the II⁺ and IV⁺ oxidationstates are also advantageous. The metal employed in the catalyst systemof the invention is most preferably from groups 4, 5 or 6 of theperiodic table, e.g. Cr, Mo, W, Ti, Zr, Hf, V, Nb or Ta. Most especiallythe metal is Cr or Ti, e.g. Cr³⁺ or Ti³⁺.

Where the metal is Cr, it has surprisingly been found that the catalystsystem of the invention is capable of making polypropylene as a powder.

The group 3 to 7 metal in the metallated procatalyst of the inventioncoordinates to the η⁵-ligand and σ or η bonds to certain atoms in thebicyclic nitrogen ligand. Where the metal forms sigma bonds with thebicyclic nitrogen ligand, only atoms Z and N can coordinate to themetal. Thus, the metal may be coordinated only to atom X, only to N orto both the Z and N atoms. The Y atom is therefore not involved incoordination with the metal.

However, if an η ligand is formed between the metal and bicyclicnitrogen group then coordination to any double bond present in bicyclicnitrogen ligand is possible. Such η bonds may be η² or η³ depending onthe nature of the bicyclic nitrogen ligand. The metal may also becoordinated by hydrogen atoms, hydrocarbyl σ-ligands (eg optionallysubstituted C₁₋₁₂ hydrocarbyl groups, such as C₁₋₁₂ alkyl, alkenyl oralkynyl groups optionally substituted by fluorine and/or aryl (egphenyl) groups), by silane groups (eg Si(CH₃)₃), by halogen atoms (egchlorine), by C₁₋₈ hydrocarbylheteroatom groups, bytri-C₁₋₈hydrocarbylsilyl groups, by bridged bis-σ-liganding groups, byamine (eg N(CH₃)₂) or imine (eg N═C or N═P groups, eg (iPr)₃P═N) groups,or by other σ-ligands known for use in metallocene (pro) catalysts.

By a σ-ligand moiety is meant a group bonded to the metal at one or moreplaces via a single atom, eg a hydrogen, halogen, silicon, carbon,oxygen, sulphur or nitrogen atom.

Examples of σ-ligands include

halogenides (e.g. chloride and fluoride), hydrogen,

triC₁₋₁₂ hydrocarbyl-silyl or -siloxy(e.g. trimethylsilyl),

triC₁₋₆ hydrocarbylphosphimido (e.g. triisopropylphosphimido),

C₁₋₁₂hydrocarbyl or hydrocarbyloxy (e.g. methyl, ethyl, phenyl, benzyland methoxy),

diC₁₋₆ hydrocarbylamido (e.g. dimethylamido and diethylamido), and

5 to 7 ring membered heterocyclyl (eg pyrrolyl, furanyl andpyrrolidinyl). Preferable σ ligands include halogens, alkyls, orchloro-amido groups.

Y preferably represents a nitrogen atom.

In the catalyst system formed from the compound of the invention, the Yatom does not sigma coordinate to the metal ion. Instead, the atom at Yserves to provide an atom whereby the bridging group X can join thebicyclic nitrogen group to the η⁵-ligand.

The Z atom, which as mentioned above may be involved in coordinationwith the metal ion, is preferably a phosphorus or nitrogen atom,especially a nitrogen atom.

In a most preferred embodiment both Y and Z are nitrogen.

The A rings (A₁ and A₂), formed partially from the atoms —Y—C—Z— or—N—C—Z— may be or different sizes but are preferably or the same size.Moreover, each ring preferably has either 5 or 6 members. Whilst therings may contain further heteroatoms selected from N, P, S or B, thisis not preferred. Thus, apart from the potential heteroatoms representedby Y and Z, the A rings are preferably formed from carbon atoms. The Arings may contain double bonds and may be aromatic but preferably therings contain no double bonds in addition to the double bond which mustbe present between the C and N in formula (I). Preferably, the rings areunsubstitued.

Thus suitable bicyclic groups include those illustrated below.

In a highly preferred embodiment the bicyclic group is formed from twofused six membered rings and Y and Z are nitrogen, i.e. the last or thefive structures above.

The η⁵-ligand may be any η⁵-ligand which forms an η-bond with thecomplexing metal ion. Suitable ligands therefore includedipyridylmethanyl, indenyl, fluorenyl or cyclopentadienyl ligands. Theη⁵-ligand is substituted by groups R₁ and (R″)_(m) as hereinbeforedefined. Hence, suitable procatalysts or use in the invention includethose of formula

wherein R₁, R″, m, X, Y, Z and rings A₁ and A₂ are as hereinbeforedefined. Alternatively, the η⁵-ligand is of formula

wherein R₁, R″, m, X, Y, Z and rings A₁ and A₂ are as hereinbeforedefined. In the above formula, the R₁ and R″ groups may be bound to anyring of the η⁵-ligand, i.e. although the R₁ group in the formulaimmediately above is depicted as being generally present on the5-membered ring, the nomenclature is intended to cover the possibilityor the R₁ group being present on the 6-membered ring.

The preferred nature of the groups R₁ and R″ varies depending on thenature or the η⁵-ligand. Where the η⁵-ligand is a cyclopentadienyl, R₁is preferably a group of formula OSiR′₃. Preferably R′ is a C₁₋₁₂hydrocarbyl group, e.g. a C₁₋₁₈ alkyl or alkenyl group, especiallymethyl or isopropyl.

Examples of suitable R′₃SiO groups in the compounds or procatalysts ofthe invention include

Where the η⁵-ligand is a cyclopentadienyl group, the OSiR′₃ group may besituated at any position on the cyclopentadienyl ring but preferably isalpha to the carbon atom involved in bridging.

The cyclopentadienyl group itself may be substituted by up to threegroups R″ and R″ preferably represents C₁₋₁₆ alkyl, especially methyl.In a highly preferred embodiment, three R″ groups are present and R″ ismethyl. Since R₁ may also represent R″ a cyclopentadienyl substituted byfour methyl groups is also within the scope of the invention.

Also within the scope of the invention are cyclopentadienyl groupswherein one of the carbon atoms not bound to the bridging group X or ifpresent the OSiR′₃ group, is replaced by a heteroatom selected fromphosphorus, silicon, nitrogen or boron. It is stressed however, thatpreferably there are no heteratoms present in the cyclopentadienyl ring.

Thus typical examples or suitable cyclopentadienyl type moietiesinclude:

Examples of particular cyclopentadienyl siloxy groups usable accordingto the invention include:

triisopropylsiloxycyclopentadienyl,

1-triisopropylsiloxy-3-methyl-cyclopentadienyl,

1-triisopropylsiloxy-3,4-dimethyl-cyclopentadienyl,

1-triisopropylsiloxy-2,3,4-trimethyl-cyclopentadienyl,

(dimethyltertbutylsiloxy)-cyclopentadienyl,

1-(dimethyltertbutylsiloxy)-3-methylycyclopentadienyl,

1-(dimethyltertbutylsiloxy)-3,4-dimethylcyclopentadienyl,

1-(dimethyltertbutylsiloxy)-2,3,4-trimethyl-cyclopentadienyl,

1-triisopropylsiloxy-2-phospholyl,

1-triisopropylsiloxy-3-phospholyl,

1-dimethyltertbutylsiloxy-2-phospholyl,

1-dimethyltertbutylsiloxy-3-phospholyl,

1-triisopropylsiloxy-2-borolyl,

1-triisopropylsiloxy-3-borolyl,

1-dimethyltertbutylsiloxy-2-borolyl,

1-dimethyltertbutylsiloxy-3-borolyl,

1-(dimethyloct-1-en-8-ylsiloxy)-3-methyl-cyclopentadienyl,

1-(dimethyloct-1-en-8-ylsiloxy)-3,4-dimethyl-cyclopentadienyl.

Where the η⁵-ligand is a dipyridylmethanyl, indenyl or fluorenyl speciesthe R₁ may also be a group of formula OSiR′₃ as hereinbefore describedbut preferably R₁ is hydrogen. R″ may represent a C₁₋₆ alkyl, especiallymethyl but again in a preferred embodiment R″ is hydrogen. Where the ηligand is indenyl, R″ may preferably represent an n-alkenyl, e.g.n-hexyl.

Examples of particular further η-ligands are well known from thetechnical and patent literature relating to metallocene olefinpolymerization catalysts, e.g. EP-A-35242 (BASF), EP-A-129368 (Exxon),EP-A-206794 (Exxon), PCT/FI97/00049 (Borealis), EP-A-318048,EP-A-643084, EP-A-69951, EP-A-410734, EP-A-128045, EP-B-35242 (BASF),EP-B-129368 (Exxon), WO97/23493, Organometallics 1995, 14, 471 andEP-B-206794 (Exxon). Further suitable η-ligands are those or formula

The bridging group X is preferably a one or two atom bridge comprisingsilicon or carbon. The bridge preferably connects to a carbon atompresent in the 5-membered ring or the η⁵-ligand. However, where theligand comprises a heteroatom such as boron, the bridge may attach tothe heteroatom or to the heteroatom's substituents. Where the bridge isformed from silicon, the bridge may be of formula —Si(R₂)₂ wherein eachR₂ independently represents a C₁₋₁₀ alkyl, C₁₋₁₀ alkenyl, aryl, e.g.phenyl, trimethylsilyl, or both R₂ groups taken together may form aring, e.g. five membered ring, with the Si. Where the bridge comprisescarbon, the bridge is preferably a one atom bridge, e.g. —CH₂— or—CH(CH₃)₂—. Suitable bridges are depicted below

In a highly preferred embodiment, compound according to the invention isof formula

wherein R′, m and R″ are as hereinbefore described.

Further typical examples of the procatalysts or the invention include:

The procatalysts of the invention may be prepared by conventionaltechniques which will be readily devised by the person skilled in theart. Conveniently for example, the procatalyst is constructed bycombining the bicyclic ligand with, for example, the siloxycyclopentadienyl ligand followed by subsequent metallation. The bridginggroup may be carried by either the bicyclic ligand or thecyclopentadienyl ligand but conveniently the bridging group is attachedto the bicyclic group first.

Where the bicyclic group is for example1.5.7-triaza[4.4.0]bicyclo-dec-5-ene this may be deprotonated by astrong base and the resulting anion reacted with a bridging group suchas dimethylsilyldichloride. The cyclopentadienyl η-ligands usedaccording to the invention may be prepared by reaction of acorresponding siloxycyclopentadiene with an organolithium compound, egmethyllithium or butyllithium. The reaction or the lithiumcyclopentadienyl species with the bicyclic ligand carrying bridiginggroup gives rise to a compound or the invention after furtherdeprotonation. These reactions are depicted in the Scheme below.

Fluorenyl and indenyl compounds of the invention may be prepared byanalogous techniques to those required to prepare the cyclopentadienylcompounds.

Where the η-ligand is a dipyridylmethanediyl, the bicyclic nitrogenligand may be reacted with a species generated as illustrated in thefollowing scheme.

Deprotonation of the product again leaves the compound of the invention.The starting material may be functionalised as necessary to haverequired substituents using conventional synthetic chemistry. It is ofcourse possible to have the dipyridylmethanediyl carry the bridginggroup using the following chemistry:

The compound can be metallated conventionally, eg by reaction with ahalide or the metal M, preferably in an organic solvent, eg ahydrocarbon or a hydrocarbon/ether mixture.

σ-ligands other than chlorine may be introduced by displacement orchlorine from an η-ligand metal chloride by reaction with appropriatenucleophilic reagent (e.g. methyl lithium or methylmagnesium chloride)or using, instead or a metal halide, a reagent such astetrakisdimethylamidotitanium or metal compounds with mixed chloro anddimethylamido ligands.

As mentioned above, the olefin polymerisation catalyst system of theinvention comprises (i) a procatalyst formed from a metallated compoundof formula (I) and (ii) an aluminium alkyl compound, or the reactionproduct thereof. While the aluminium alkyl compound may be an aluminiumtrialkyl (eg triethylaluminium (TEA)) or an aluminium dialkyl halide (egdiethyl aluminium chloride (DEAC)), it is preferably an alumoxane,particularly an alumoxane other than MAO, most preferably anisobutylalumoxane, eg TIBAO (tetraisobutylalumoxane) or HIBAO(hexaisobutylalumoxane). Alternatively however the alkylated (egmethylated) metallocene procatalysts of the invention (e.g. compounds orformula V wherein Z is alkyl) may be used with other cocatalysts, egboron compounds such as B(C₆F₅)₃, C₆H₅N(CH₃)₂H:B(C₆F₅)₄,(C₆H₅)₃C:B(C₆F₅)₄ or Ni (CN)₄[B(C₆F₅)₃]₄ ²—.

The metallocene procatalyst and cocatalyst may be introduced into thepolymerization reactor separately or together or, more preferably theyare pre-reacted and their reaction product is introduced into thepolymerization reactor.

If desired the procatalyst, procatalyst/cocatalyst mixture or aprocatalyst/cocatalyst reaction product may be used in unsupported formor it may be precipitated and used as such. However the metalloceneprocatalyst or its reaction product with the cocatalyst is preferablyintroduced into the polymerization reactor in supported form, egimpregnated into a porous particulate support.

The particulate support material used is preferably an organic orinorganic material, e.g. a polymer(such as for example polyethylene,polypropylene, an ethylene-propylene copolymer, another polyolefin orpolystyrene or a combination thereof). Such polymeric supports may beformed by precipitating a polymer or by a prepolymerization, eg ofmonomers used in the polymerization for which the catalyst is intended.However, the support is especially preferably a metal or pseudo metaloxide such as silica, alumina or zirconia or a mixed oxide such assilica-alumina, in particular silica, alumina or silica-alumina.Particularly preferably, the support material is acidic, e.g. having anacidity greater than or equal to silica, more preferably greater than orequal to silica-alumina and even more preferably greater than or equalto alumina. The acidity of the support material can be studied andcompared using the TPD (temperature programmed desorption or gas)method. Generally the gas used will be ammonia. The more acidic thesupport, the higher will be its capacity to adsorb ammonia gas. Afterbeing saturated with ammonia, the sample or support material is heatedin a controlled fashion and the quantity of ammonia desorbed is measuredas a function of temperature.

Especially preferably the support is a porous material so that themetallocene may be loaded into the pores of the support, e.g. using aprocess analogous to those described in WO94/14856 (Mobil), WO95/12622(Borealis) and WO96/00243 (Exxon). The particle size is not critical butis preferably in the range 5 to 200 μm, more preferably 20 to 80 μm.

Before loading, the particulate support material is preferably calcined,ie heat treated, preferably under a non-reactive gas such as nitrogen.This treatment is preferably at a temperature in excess or 100° C., morepreferably 200° C. or higher, e.g. 200-800° C., particularly about 300°C. The calcination treatment is preferably effected for several hours,e.g. 2 to 30 hours, more preferably about 10 hours.

The support may be treated with an alkylating agent before being loadedwith the metallocene. Treatment with the alkylating agent may beeffected using an alkylating agent in a gas or liquid phase, e.g. in anorganic solvent for the alkylating agent. The alkylating agent may beany agent capable of introducing alkyl groups, preferably C₁₋₁₆ alkylgroups and most especially preferably methyl groups. Such agents arewell known in the field of synthetic organic chemistry. Preferably thealkylating agent is an organometallic compound, especially anorganoaluminium compound (such as trimethylaluminium (TMA), dimethylaluminium chloride, triethylaluminium) or a compound such as methyllithium, dimethyl magnesium, triethylboron, etc.

The quantity of alkylating agent used will depend upon the number ofactive sites on the surface of the carrier. Thus for example, for asilica support, surface hydroxyls are capable of reacting with thealkylating agent. In general, an excess of alkylating agent ispreferably used with any unreacted alkylating agent subsequently beingwashed away.

Where an organoaluminium alkylating agent is used, this is preferablyused in a quantity sufficient to provide a loading of at least 0.1 mmolAl/g carrier, especially at least 0.5 mmol Al/g, more especially atleast 0.7 mmol Al/g, more preferably at least 1.4 mmol Al/g carrier, andstill more preferably 2 to 3 mmol Al/g carrier. Where the surface areaof the carrier is particularly high, lower aluminium loadings may beused. Thus for example particularly preferred aluminium loadings with asurface area of 300-400 m²/g carrier may range from 0.5 to 3 mmol Al/gcarrier while at surface areas of 700-800 m²/g carrier the particularlypreferred range will be lower.

Following treatment of the support material with the alkylating agent,the support is preferably removed from the treatment fluid and anyexcess treatment fluid is allowed to drain off.

The optionally alkylated support material is loaded with theprocatalyst, preferably using a solution of the procatalyst in anorganic solvent therefor, e.g. as described in the patent publicationsreferred to above. Preferably, the volume of procatalyst solution usedis from 50 to 500% or the pore volume of the carrier, more especiallypreferably 80 to 120%. The concentration of procatalyst compound in thesolution used can vary from dilute to saturated depending on the amountof metallocene active sites that it is desired be loaded into thecarrier pores.

The active metal (ie. the metal or the procatalyst) is preferably loadedonto the support material at from 0.1 to 4%, preferably 0.5 to 3.0%,especially 1.0 to 2.0%, by weight metal relative to the dry weight ofthe support material.

After loading of the procatalyst onto the support material, the loadedsupport may be recovered for use in olefin polymerization, e.g. byseparation of any excess procatalyst solution and if desired drying orthe loaded support, optionally at elevated temperatures, e.g. 25 to 80°C.

Alternatively, a cocatalyst, e.g. an alumoxane or an ionic catalystactivator (such as a boron or aluminium compound, especially afluoroborate) may also be mixed with or loaded onto the catalyst supportmaterial. This may be done subsequently or more preferablysimultaneously to loading of the procatalyst, for example by includingthe cocatalyst in the solution of the procatalyst or, by contacting theprocatalyst loaded support material with a solution of the cocatalyst orcatalyst activator, e.g. a solution in an organic solvent. Alternativelyhowever any such further material may be added to the procatalyst loadedsupport material in the polymerization reactor or shortly before dosingof the catalyst material into the reactor.

In this regard, as an alternative to an alumoxane it may be preferred touse a fluoroborate catalyst activator, especially a B(C₆F₅)₃ or moreespecially a ^(⊖)B(C₆F₅)₄ compound, such as C₆H₅N(CH₃)₂H:B(C₆F₅)₄ or(C₆H₅)₃C:B(C₆F₅)₄. Other borates or general formula (cation⁺)_(a)(borate⁻)_(b) where a and b are positive numbers, may also be used.

Where such a cocatalyst or catalyst activator is used, it is preferablyused in a mole ratio to the metallocene of from 0.1:1 to 10000:1,especially 1:1 to 50:1, particularly 1:2 to 30:1. More particularly,where an alumoxane cocatalyst is used, then for an unsupported catalystthe aluminium:metallocene metal (M) molar ratio is conveniently 2:1 to10000:1, preferably 50:1 to 1000:1. Where the catalyst is supported theAl:M molar ratio is conveniently 2:1 to 10000:1 preferably 50:1 to400:1. Where a borane cocatalyst (catalyst activator) is used, the B:Mmolar ratio is conveniently 2:1 to 1:2, preferably 9:10 to 10:9,especially 1:1. When a neutral triarylboron type cocatalyst is used theB:M molar ratio is typically 1:2 to 500:1, however some aluminium alkylwould normally also be used. When using ionic tetraaryl boratecompounds, it is preferred to use carbonium rather than ammoniumcounterions or to use B:M molar ratio below 1:1.

Where the further material is loaded onto the procatalyst loaded supportmaterial, the support may be recovered and if desired dried before usein olefin polymerization.

The olefin polymerized in the method or the invention is preferablyethylene or an alpha-olefin or a mixture or ethylene and an α-olefin ora mixture of alpha olefins, for example C₂₋₂₀ olefins, e.g. ethylene,propene, n-but-l-ene, n-hex-l-ene, 4-methyl-pent-l-ene, n-oct-l-ene-etc.The olefins polymerized in the method of the invention may include anycompound which includes unsaturated polymerizable groups. Thus forexample unsaturated compounds, such as C₆₋₂₀ olefins (including cyclicand polycyclic olefins (e.g. norbornene)), and polyenes, especiallyC₆₋₂₀ dienes, may be included in a comonomer mixture with lower olefins,e.g. C₂₋₅ α-olefins. Diolefins (ie. dienes) are suitably used forintroducing long chain branching into the resultant polymer. Examples ofsuch dienes include α,ω linear dienes such as 1,5-hexadiene,1,6-heptadiene, 1,8-nonadiene, 1,9-decadiene, etc.

In general, where the polymer being produced is a homopolymer it willpreferably be polyethylene or polypropylene. Where the polymer beingproduced is a copolymer it will likewise preferably be an ethylene orpropylene copolymer with ethylene or propylene making up the majorproportion (by number and more preferably by weight) or the monomerresidues. Comonomers, such as C₄₋₆ alkenes, will generally beincorporated to contribute to the mechanical strength or the polymerproduct.

Usually metallocene catalysts yield relatively narrow molecular weightdistribution polymers; however, if desired, the nature or themonomer/monomer mixture and the polymerization conditions may be changedduring the polymerization process so as to produce a broad bimodal ormultimodal molecular weight distribution (MWD) in the final polymerproduct. In such a broad MWD product, the higher molecular weightcomponent contributes to the strength or the end product while the lowermolecular weight component contributes to the processability of theproduct, e.g. enabling the product to be used in extrusion and blowmoulding processes, for example for the preparation of tubes, pipes,containers, etc.

A multimodal MWD can be produced using a catalyst material with two ormore different types of active polymerization sites, e.g. with one suchsite provided by the metallocene on the support and further sites beingprovided by further catalysts, e.g. Ziegler catalysts, othermetallocenes, etc. included in the catalyst material.

Polymerization in the method of the invention may be effected in one ormore, e.g. 1, 2 or 3, polymerization reactors, using conventionalpolymerization techniques, e.g. gas phase, solution phase, slurry orbulk polymerization.

In general, a combination of slurry (or bulk) and at least one gas phasereactor is often preferred, particularly with the reactor order beingslurry (or bulk) then one or more gas phase.

For slurry reactors, the reaction temperature will generally be in therange 60 to 110° C. (e.g. 85-110° C.), the reactor pressure willgenerally be in the range 5 to 80 bar (e.g. 50-65 bar), and theresidence time will generally be in the range 0.3 to 5 hours (e.g. 0.5to 2 hours). The diluent used will generally be an aliphatic hydrocarbonhaving a boiling point in the range −70 to +100° C. In such reactors,polymerization may if desired be effected under supercriticalconditions.

For gas phase reactors, the reaction temperature used will generally bein the range 60 to 115° C. (e.g. 70 to 110° C.), the reactor pressurewill generally be in the range 10 to 25 bar, and the residence time willgenerally be 1 to 8 hours. The gas used will commonly be a non-reactivegas such as nitrogen together with monomer(e.g. ethylene).

For solution phase reactors, the reaction temperature used willgenerally be in the range 130 to 270° C., the reactor pressure willgenerally be in the range 20 to 400 bar and the residence time willgenerally be in the range 0.1 to 1 hour. The solvent used will commonlybe a hydrocarbon with a boiling point in the range 80-200° C.

Generally the quantity of catalyst used will depend upon the nature orthe catalyst, the reactor types and conditions and the propertiesdesired for the polymer product. Conventional catalyst quantities, suchas described in the publications referred to herein, may be used.

All publications referred to herein are hereby incorporated byreference.

EXPERIMENTAL

General Considerations

All operations were carried out in argon or nitrogen atmosphere usingstandard Schlenk, vacuum and dry box techniques. Solvents were driedwith potassium benzophenone ketyl and distilled under argon prior touse. 1.5.7-triaza[4.4.0]bicyclo-dec-5-ene (TAB-H) (Fluka) anddipyridylketone (DPM-H) (Fluka) were used as purchased. Benzyl potassiumwas prepared according to Schlosser, M. and Hartmann, J. Angew. Chem1973, 85, 544-545. CrCl₃(THF)₃ and TiCl₃(THF)₃ were prepared accordingto W. A. Herrmann and G. Brauer, Synthetic Methods or Organometallic andInorganic Chemistry, Vol. 1: Literature, Laboratory Techniques andCommon Starting Materials, Thieme 1996. 1H- and 13C-NMR spectra wererecorded using JEOL JNM-EX 270 MHz FT NMR spectrometer withtetramethylsilane (TMS) as an internal reference. 13C-CPMAS NMR and themass spectra were recorded at Fortum Oil and Gas Oy, Analytical Researchdepartment. The CPMAS-NMR spectra were recorded using ChemagneticsInfinity 270 MHz equipment and the direct inlet MS spectra were producedby VG TRIO 2 quadrupole mass spectrometer in electron impact ionisationmode (EIMS) (70 eV). The GC-MS analyses were performed using HewlettPackard 6890/5973 Mass Selective Detector in electron impact ionisationmode (70 eV) equipped with a silica capillary column (30 m×0.25 mmi.d.). The FTIR spectra were recorded at Borealis Analytical Researchdepartment using Perkin-Elmer Spectrum 2000 spectrometer with inertdiamond ATR accessory and 4 cm-1 resolution. Thermogravic measurements(TG) were recorded using GWB METTLER TG50 Termobalance and theDifferential Scanning Calorimetry (DSC) and melting point analyses usingGWB METTLER DSC-30 under inert conditions at Borealis AnalyticalResearch department. The polymerization tests were carried out usingMAO, 30% solution in toluene purhased from Albermarle. Testpolymerizations were carried out in pentane at 60° C. and at 80° C. withhydrogen present using an Al/M ratio or 1000 unless otherwise stated. ABüchi 2 L stirred reactor with mantle heating was used for thepolymerization tests.

EXAMPLE 1

Synthesis of (1.5.7-triaz[4.4.0]bicyclo-dec-5-enyl) potassium, C₇H₁₂KN₃

Red solid benzyl potassium (9.6 g, 73.3 mmol) was added into thesolution of 1.5.7-triaza[4.4.0]bicyclo-dec-5-ene (10.2 g, 73.3 mmol) in350 ml of dry toluene at −40° C. The temperature was allowed to warm toroom temperature and the mixture stirred for 16 hours. The colourchanged via red to a white slurry. The solvents were removed in avacuum, the product washed with 3×60 ml of ether and dried in a vacuumto obtain 10.1 g (78%) of white powder. ¹H-NMR in THF-d₈; δ: 3.17 (t,4H); 2.98 (t, 4H); 1.69 (t, 4H). The potassium salt product could not beanalysed with MS. Elemental analysis calc.: C 47.4%, H 6.8%, N 23.7%, K22.1%. Elemental analysis found: C 46.0%, H 6.4%, N 23.1%.

EXAMPLE 2

Synthesis of triazabicyclodec-ene-yl-1-dimethylsilylchlorideC₉H₁₈ClN₃Si.

1.5.7-triaza[4.4.0]bicyclo-dec-5-enyl potassium 13.0 g (73.1 mmol)dissolved in 200 mL of THF was added into a solution of 55 mL (438.6mmol) of Me₂SiCl₂ in 50 mL THF over 3 hours at ambient temperature.Colour changed from yellow to dark yellow. The solution was stirred for2 hours at ambient temperature after which the mixture containing agelish precipitate of KCl was filtrated and washed with 2×30 mL of THF.Solvent was removed under vacuum to obtain an off yellow solid which wasextracted with 3×30 mL of pentane and and filtrated. The product waspurified by recrystallization and filtration from cold (−30° C.) pentaneyielding colorless, needle-like crystals. Yield 12.9 g (76.4%). ¹H-NMRCDCl₃ δ: 3.16 (t, 4H), 3.11 (t, 4H), 1.88 (t, 4H), 0.46 (s, 6H). ¹³C-NMRCDCl₃δ: 154.9, 45.3, 38.6, 23.3, 7.9. EIMS analysis showed thedecomposition pattern of the parent ion of the title compoundC₉H₁₈ClN₃Si M⁺=231.80 g mol⁻¹. Elemental analysis calc. C 46.63%, H7.83%, N 18.13%, Cl 15.29%, Si 12.12%; Found. C 46.52%, H 7.80%, N18.24%, Cl 15.15%, Si 12.05%.

EXAMPLE 3

t-Butyldimethylsiloxy-3,4-dimethylcyclopentadienyl lithium

40.0 g (465 mmol) of crotonic acid (Fluka 28010), 25.1 g (418 mmol) ofisopropanol (Merck 1.09634.2500), 200 mL of benzene, 4.2 g of conc.H₂SO₄ and 2.1 g of para-toluene sulfonic acid was charged to a 500 mLflask equipped with a magnetic stirrer bar and Dean-Stark waterseparator. The mixture was refluxed until water formation ceased. 200 mLof ether was added to the mixture, and then washed with several portionsof NaHCO₃ (aq., sat.) until the the acid was neutralized. Organic phasewas separated, dried with MgSO₄ and filtered. Solvent was removed underreduced pressure and the remainder distilled at 95° C. to give 30.5 g ofisopropylcrotonate. Yield 57%. ¹H-NMR (CDCl₃): 6.95 (dq, 1H), 5.82 (d,1H), 5.05 (sept, 1H), 1.88 (d, 3H), 1.25 (d, 6H).

811 g of polyphosphoric acid (Fluka 81340) was loaded to a round bottomflask equipped with a reflux condenser and a magnetic stirrer bar andheated to 100° C. 104 g (810 mmol) of isopropylcrotonate was added tothe flask and the mixture was stirred for 2 hours at 100° C. Theresulted mixture was poured to >>1,5 kg of crushed ice. At roomtemperature the mixture was saturated with NH₄Cl and extracted with4×100 mL of ether. The combined ether fractions were dried over MgSO₄and filtered. Solvent was removed under reduced pressure and theremainder distilled (0.2 mbar, 33° C., bath 90° C.) to give 47.99 g of3,4-dimethylcyclopentenone. Yield 54%. ¹H-NMR (CDCl₃): 5.86 (s, 1H),2.80 (m, 1H), 2.64 (dd, 1H), 2.07 (s, 3H), 2.00 (dd, 1H), 1.18 (d, 3H).

12.23 g (111.0 mmol) of 3,4-dimethylcyclopentenone, 11.31 g (111.8 mmol)of triethylamine dried with molecular sieves and 300 mL of dry pentanewere mixed at room temperature. During 13 minutes 29.44 g (111.4 mmol)of t-butyldimethylsilyltrifluoromethylsulfonate (Fluka 97742) was addedto the mixture. After strirring for 2.5 hour the supernatant pentanefraction was separated, solvent removed under reduced pressure and theremainder distilled (0.03 mbar, 34-40° C., bath 100° C.) resulting in19.74 g of isomer isomer mixture oft-butyldimethylsiloxy-3,4-dimethylcyclopentadienes. Yield 79%. ¹H-NMRspectrum was complicated due to presence of at least 3 isomers. Theproduct was characterised by GC/MS technique, which showed presence ofthree components (GC) each showing M+ peak at 224 (MS).

10 g (44.6 mmol) of isomer mixture oft-butyldimethyl-siloxy-3,4-dimethylcyclopentadienes was mixed with 200mL of pentane at room temperature. At −20° C. 28.4 mL (44.6 mmol) of1.57 M t-butyllithium solution in hexanes (Acros 18128-0900) was added.Temperature was increased to 20° C. during 15 hours while stirring. Theresulted solid product was separated by filtration and washed with 2×100mL of pentane. Remaining solvent was removed under reduced pressure.7.07 g of t-butyl-dimethylsiloxy-3,4-dimethylcyclopentadienyl lithiumwas isolated. Yield 69%. ¹H-NMR (THF-d₈): 4.88 (s, 2H), 1.95 (s, 6H),0.95 (s, 9H), 0.08 (s, 6H).

EXAMPLE 4

Synthesis of Tri-isopropylsiloxycyclopentadienyl Lithium

Triisopropylsiloxycyclopentadiene was prepared analogously to example 3using triisopropylsilyl-trifluoromethylsulfonate (Fluka 91746) andcyclopent-2-enone (Fluka 29827) as starting materials. It was notisolated but lithiated immediately to avoid spontaneous Diels-Alderdimerisation of the product. Lithiation was performed analogously toexample 3 and afforded triisopropylsiloxycyclopentadienyl lithium in 81%yield. ¹H-NMR (THF-d₈): 5.22 (m, 2H), 5.17 (m, 2H), 1.11 (m, 3H), 1.04(d, 18H).

EXAMPLE 5

Synthesis ofTriazabicyclodec-ene-yl-1-dimethylsilyl-dimethyl-tertbutylsiloxyDimethylcyclopentadiene (mixture of isomers) C₂₂H₄₁N₃OSi₂

1.2 g (5.21 mmol) of t-butyldimethylsiloxy-3,4-dimethylcyclopentadienyllithium dissolved in 100 mL of THF was added over 1 h into a solution of1.2 g (5.21 mmol) of triazabicyclodec-ene-yl-1-dimethylsilylchloride in50 mL of THF at −70° C. to give an orange transparent solution. Thesolution was refluxed for 16 hours after which the solvent was removedunder vacuum. The product was extracted into pentane, filtrated andcooled to −30° C. for 16 hours. Trace insolubilities were filtrated offat −30° C. and the solvent removed under vacuum to give 98% pure, brownoily mixture of double bond and stereoisomers. Yield 1.6 g (73.3%). TheEIMS analysis showed the decomposition pattern of the parent ion of thetitle compound C₂₂H₄₁N₃OSi₂ M⁺=419.76 g mol⁻¹, fragmentation peaks at404, 270, 224 and 196. ¹H-NMR of the major isomer in THF-d₈ δ: 5.02 (s,1H) 3.41 (s, 1H) 3.18 (m, 4H) 3.06 (m, 4H) 2.02 (s, 3H) 1.95 (s, 3H)1.78 (m, 4H) 0.97 (s, 9H) 0.24 (s, 3H), 0.22 (s, 3H), 0.19 (s, 3H), 0.10(s, 3H). ¹³C-NMR THF-d₈ δ: 160.9, 151.6, 131.7, 124.6, 110.6, 95.5,53.0, 48.9, 43.3, 27.0, 26.4, 24.7, 13.0, 0.9, −4.1, −4.6.

EXAMPLE 6

Synthesis oftriazabicyclodec-ene-yl-1-dimethylsilyl-dimethyl-tertbutylsiloxydimethylcyclopentadienyl chromium dichloride C₂₂H₄₀Cl₂CrN₃OSi₂

1.8 mL of MeLi (1.6 M solution in diethyl ether, 3.34 mmol) was addedinto a solution of 1.6 g (3.34 mmol) oftriazabicyclodec-ene-yl-1-dimethylsilyl-dimethyl-tertbutylsiloxydimethylcyclopentadiene in 50 mL THF at +50° C. over 5 minutes andstirred at ambient temperature for 16 hours. CrCl₃(THF)₃ (3.34 mmol)dissolved in THF was added over 40 minutes at −50° C. to give a darkblue solution which was stirred at ambient temperature for 16 hours.Solvents were removed under vacuum and the product extracted in toluene,filtered and evaporated. The raw product was purified by washing withcold pentane. Yield 1.0 g (52.2%) of dark blue microcrystalline solid.The compound was paramagnetic, NMR identification was not possible. TheEIMS analysis showed the decomposition pattern of the parent ion of thetitle compound C₂₂H₄₀Cl₂CrN₃OSi₂ M⁺=541.65 g mol⁻¹, fragmentation peaksat 504, 468, 418, 287, 224, 196 and 138. Melting point: 145° C. (broadpeak in DSC). TG analysis (from 30° C. to 891° C., 10° C./min) showed57.7% loss of weight in a one phase process at 286° C. averaged deltatemperature. Crystals suitable for X-ray analysis were not obtainedbecause of the presence of the two stereoisomers (rac and meso type)which resulted in the precipitation of microcrystalline solid. Elementalanalysis calc. C 48.78%, H 7.44%, N 7.76%, Cl 13.09%, Si 10.37%, Cr9.60%; Found C 49.02%, H 7.56%, N 7.94%, Cl 12.91%, Si 10.11%, Cr 9.44%.

EXAMPLE 7

Synthesis of Triazabicyclodec-ene-yl-1-dimethylsilyl-tri-isopropylsiloxyCyclopentadiene (Mixture of Isomers) C₂₃H₄₃N₃OSi₂

3.2 g (12.3 mmol, 92.6%) of tri-isopropylsiloxy-cyclopentadienyl lithiumdissolved in 70 mL of THF was added over 40 minutes into a solution of2.8 g (12.3 mmol) of triazabicyclodec-ene-yl-1-dimethylsilylchloride in70 mL of THF at −70° C. to give a red mixture. The mixture was refluxedfor 16 hours after which the solvent was removed under vacuum. Theproduct was extracted into pentane, filtrated and the filtrate cooled to−30° C. for 16 hours after which the insolubles were filtered off at−30° C. The filtrate was then cooled to −70° C. for 6 h and the traceinsolubles filtrated off at −70° C. The pentane was then removed undervacuum to give a dark brown, viscous oily mixture of double bond andregioisomers. Yield 3.1 g (57.6%). The EIMS analysis showed thedecomposition pattern of the parent ion of the title compoundC₂₃H₄₃N₃OSi₂ M⁺=433.78 g mol⁻¹, fragmentation peaks at 418, 390, 238 and196. ¹H-NMR major isomer in THF-d₈ δ: 6.39 (m, 1H) 6.21 (m, 1H) 5.62 (m,1H) 3.19 (m, 4H) 3.08 (m, 4H) 2.92 (m, 1H) 1.80 (m, 4H) 1.20 (m, 3H)1.18 (s, 18H) 0.25 (s, 6H). ¹³C-NMR major isomer (1,3-substitutedregioisomer) in THF-d₈ δ: 149.0, 131.8, 130.8, 130.0, 105.0, 102.0,47.0, 41.2, 22.7, 16.2, 11.2, 0.4. The compound decomposed during theelemental analysis sample preparation.

EXAMPLE 8

Synthesis of triazabicyclodec-ene-yl-1-dimethylsilyl-tri-isopropylsiloxycyclopentadienyl chromium dichloride (Mixture of Isomers)C₂₃H₄₂N₃Cl₂CrOSi₂

3.7 mL of MeLi (1.9 M solution in diethyl ether, 7.04 mmol) was addedinto a solution of 3.1 g (7.04 mmol) oftriazabicyclodec-ene-yl-1-dimethylsilyl-tri-isopropylsiloxy-cyclopentadienein 70 mL THF at +50° C. over 5 minutes and stirred at ambienttemperature for 16 hours. CrCl₃(THF)₃ (7.04 mmol) dissolved in 50 mL THFwas added over 30 minutes at −30° C. to give a dark blue-green solutionwhich was stirred at ambient temperature for 16 hours. Solvents wereremoved under vacuum and the product extracted in toluene, filtered andevaporated. The raw product was purified by washing with cold pentane.Yield 1.9 g (48.6%) of blue-green microcrystalline solid. The compoundwas paramagnetic, NMR identification was not possible. The EIMS analysisshowed the decomposition pattern of the parent ion of the title compoundC₂₃H₄₂Cl₂CrN₃OSi₂ M⁺=555.68 g mold⁻¹, fragmentation peaks at 499, 477,238, 192 and 178. Melting point: 170.9° C. (broad peak in DSC). TGanalysis (from 30° C. to 891° C., 10° C./min) showed 55.2% loss ofweight in a two phase process at 242° C. averaged delta temperature. Mp170.9° C. Crystals suitable for X-ray analysis were not obtained becauseof the presence or the two stereoisomers (rac and meso type) whichresulted in the precipitation of microcrystalline solid. Elementalanalysis calc. C 49.71%, H 7.62%, N 7.56%, Cl 12.76%, Cr 9.36%, O 2.88%,Si 10.11%; Found C 49.50%, H 7.65%, N 7.31%, Cl 12.93%, Si 9.98%, Cr9.48%.

EXAMPLE 9

Synthesis of Triazabicyclodec-ene-yl-1-dimethylsilyl-fluorene C₂₂H₂₇N₃Si

Fluorenyllithium (prepared from fluorene via treatment of butyllithium)0.7 g (4.08 mmol) dissolved in 50 mL of THF was added over 30 minutesinto a solution of 0.9 g (4.08 mmol) oftriazabicyclodec-ene-yl-1-dimethyl-silylchloride in 50 mL of THF at −70°C. The yellowish solution was stirred at ambient temperature for 16hours after which the solvent was removed under vacuum. The product wasextracted into pentane, filtrated and cooled to −30° C. for 16 hours.The product precipitated as yellowish transparent crystals which werefiltrated and dried in a vacuum. Yield 1.1 g (73.8%). The EIMS analysisshowed the decomposition pattern of the parent ion of the title compoundC₂₂H₄₁N₃OSi₂ M⁺=361.56 g mol⁻¹, fragmentation peaks at 346, 196, 165 and138. ¹H-NMR in CDCl₃ δ: 7.90 (d, 2H), 7.58 (d, 2H), 7.38 (dd 2H) 7.30(dd, 2H), 4.95 (s, 1H) 3.22 (t, 4H) 3.19 (t, 4H) 1.91 (q, 4H) −0.1 (s,6H). ¹³C-NMR in CDCl₃ δ: 161.3, 146.3, 140.7, 125.7, 124.7, 124.3,119.5, 48.3, 43.2, 42.7, 23.8, −2.5.

EXAMPLE 10

Synthesis of triazabicyclodec-ene-yl-1-dimethylsilyl-fluorenyl chromiumdichloride C₂₂H₂₆Cl₂CrN₃Si (Descriptive Example)

1.7 mL of methyl lithium (2.94 mmol, 1.76 M solution in diethyl ether)was added at −30° C. into a solution oftriazabicyclodec-ene-yl-1-dimethylsilyl-fluorene 1.1 g (2.94 mmol) in 50mL of THF. The solution became bright neon yellow and yellowishprecipitate formed. The mixture was stirred at ambient temperature for16 hours. Then CrCl₃(THF)₃ (2.94 mmol) dissolved in 50 mL THF was addedinto the solution at −30° C. and the mixture stirred at ambienttemparature for 16 hours. Solvents were removed under a vacuum and theproduct extracted in toluene, filtered and evaporated. The paramagneticproduct was purified by washing with cold pentane and evaporated.

EXAMPLE 11

Synthesis of triazabicyclodec-ene-yl-1-diphenylsilylchlorideC₁₉H₂₂ClN₃Si

1.5.7-Triaza[4.4.0]bicyclo-dec-5-enyl potassium 3.0 g (16.9 mmol)dissolved in 50 mL of THF was added into a solution of 21 mL (101.5mmol) of Ph₂SiCl₂ in 50 mL THF over 3 hours at ambient temperature.Colour changed from whitish to light yellow. The solution was stirredfor 2 hours at ambient temperature after which the mixture containing agelish precipitate of KCl was filtrated and washed with 2×30 mL of THF.Solvents were removed under vacuum to obtain a slightly viscous liquid.Then 50 mL of pentane was added to the filtrate and the precipitatedproduct separated by filtration and washed with 2×30 mL of more pentane.Yield 5.2 g (87.3%) of white solid. ¹H-NMR CDCl₃ δ: 7.52 (dd, 4H), 7.34(d, 2H), 7.32 (d, 4H), 3.25 (m, 4H), 3.15 (t, 4H), 1.96 (q, 4H). ¹³C-NMRCDCl₃ δ: 155.1, 141.0, 134.0, 128.3, 127.2, 46.6, 38.8, 23.2. The EIMSanalysis showed the decomposition pattern of the parent ion of the titlecompound C₁₉H₂₂ClN₃Si M⁺=355.94 g mol⁻¹, frgamentation peaks at 320, 278and 138. Elemental analysis calc. C 64.11%, H 6.23%, N 11.81%, Cl 9.96%,Si 7.89%; Found C 63.89%, H 6.20%, N 11.97%, Cl 9.90%, Si 7.74%.

EXAMPLE 12

Synthesis oftriazabicyclodec-ene-yl-1-diphenylsilyl-tetramethylcyclopentadieneC₂₈H₃₅N₃Si

Tetramethylcyclopentadienyl lithium 1.04 g (8.15 mmol) (prepared fromtetramethylcyclopentadiene via treatment of n-butyllithium) dissolved in50 mL THF was added into a solution oftriazabicyclodec-ene-yl-1-diphenyl-silylchloride in 50 mL of THF over 20minutes at −30° C. The mixture was stirred at ambient temperature for 16hours, after which the solvents were removed under vacuum, the productextracted in pentane, filtered and evaporated. Yield 2.2 g (61.1%) ofwhite solid. The EIMS analysis shows the decomposition pattern of theparent of the title compound C₂₈H₃₅N₃Si M⁺441.69 g mol⁻¹. ¹H-NMR THF-d₈δ: 7.54 (d, 4H), 7.22 (m, 4H), 7.20 (d, 4H), 4.21 (s, 1H), 3.17 (t, 4H),3.03 (t, 4H), 1.83 (s, 6H), 1.75 (m, 4H), 1.42 (s, 6H). ¹³C-NMR THF-d₈δ: 151.9, 136.8, 136.7, 136.6, 133.3, 128.9, 126.9, 54.8, 48.6, 43.4,24.7, 14.5, 11.6. Elemental analysis calc. C 76.14%, H 7.99%, N 9.51%,Si 6.36%; Found C 76.04%, H 8.13%, N 9.54%, Si 6.38%.

EXAMPLE 13

Synthesis oftriazabicyclodec-ene-yl-1-diphenylsilyl-tetramethylcyclopentadienechromium dichloride C₂₈H₃₄Cl₂CrN₃Si

4.6 mL of methyl lithium (8.15 mmol, 1.76 M solution in diethyl ether)was added into a solution oftriazabicyclodec-ene-yl-1-diphenylsilyl-tetramethylcyclopentadiene in 50mL of THF at −30° C. The solution was stirred at ambient temperature for16 hours. A whitish precipitate formed. Then CrCl₃(THF)₃ dissolved in 50mL of THF (8.15 mmol) was added over 30 minutes at −30° C., and themixture stirred 16 hours at ambient temperature. The solvent was removedunder vacuum and the product extracted in toluene, filtered andevaporated. EIMS M®=563.59 g mol⁻¹. Elemental analysis calc. C 59.67%, H6.08%, N 7.46%, Cl 12.58%, Si 4.98%, Cr 9.23%; Found C 59.42%, H 6.23%,N 7.52%, Cl 12.82%, Si 5.05%, Cr 9.35%.

EXAMPLE 14

Synthesis of Trimethylsiloxycyclopentadiene

9.1 g (111.0 mmol) of cyclopent-2-en-1-one (Fluka 29827), 11.31 g (111.8mmol) of triethylamine dried with molecular sieves and 300 mL of drypentane are mixed at room temperature. Over 13 minutes 24.75 g (111.4mmol) of trimethylsilyl-trifluoromethylsulfonate (Fluka 91741) is addedto the mixture. After strirring for 2.5 hour the supernatant pentanefraction is separated, solvent removed under reduced pressure and theremainder distilled under reduced pressure resulting in an isomermixture of trimethylsiloxycyclopentadienes. The product is characterisedby ¹H-NMR and GC/MS⁺. Trimethylsiloxycyclopentadienyl lithium isprepared as described in the last section of example 3 by using t-BuLi.

Trimethylsiloxycyclopentadiene can also be synthesised according to thedescription in Acta. Chem. Scandinavica, 43, 1989, 188-92 (Scheme 2).1.74 g of LiBr (20 mmol, dried under vacuum at 400° C.) is dissolved in5.55 g of THF (77 mmol). At −15° C., 1.54 g of chlorotrimethylsilane (15mmol), 1.23 g of cyclopent-2-en-1-one (15 mmol) and 1.51 g oftriethylamine (15 mmol, dry) are added to the solution. After 1 hour at−15° C. and 24 hours at +40° C. the crude product is isolated by lowtemperature aquous NaCl/NaHCO₃ and pentane extractions. The crudetrimethylsiloxycyclopentadienes are purified by distillation underreduced pressure. Trimethylsiloxycyclopentadienyl lithium is prepared asdescribed in the last section of example 3 by using t-BuLi.

EXAMPLE 15

Synthesis oftriazabicyclodec-ene-yl-1-diphenylsilyl-trimethylsiloxycyclopentadieneC₂₇H₃₅N₃OSi₂

Trimethylsiloxycyclopentadienyl lithium (8.15 mmol) (prepared fromtrimethylsiloxycyclopentadiene via treatment of t-butyllithium)dissolved in 50 mL THF is added into a solution oftriazabicyclodec-ene-yl-1-diphenylsilylchloride in 50 mL of THF over 20minutes at −30° C. The mixture is stirred at ambient temperature for 16hours, after which the solvents are removed under vacuum, the productextracted in pentane, filtered and the major kinetically formed isomerwith 1,3-substitution pattern of the siloxy and the bridge subtituentson the Cp ring is obtained via recrystallization from cold pentane.

EXAMPLE 16

Synthesis oftriazabicyclodec-ene-yl-1-diphenylsilyl-trimethylsiloxycyclopentadienylchromium dichloride C₂₇H₃₄Cl₂CrN₃OSi₂

Methyl lithium (8.15 mmol, 1.76 M solution in diethyl ether) is addedinto a solution oftriazabicyclodec-ene-yl-1-diphenylsilyl-tetramethylcyclopentadiene in 50mL of THF at −30° C. The solution is stirred at ambient temperature for16 hours. A whitish precipitate forms. Then CrCl₃(THF)₃ dissolved in 50mL of THF (8.15 mmol) is added over 30 minutes at −30° C., and themixture stirred 16 hours at ambient temperature. The solvent is removedunder vacuum and the product extracted in toluene, filtered andevaporated to give a blue solid product.

EXAMPLE 17

Synthesis of Dipyridin-2-ylmethane C₁₁H₁₀N₂

Solid KOH (9.4 g, 167.7 mmol) was dissolved in 15 mL of distilled waterand poured into an autoclave reactor (Parr pressure reactor) undernitrogen atmosphere. Di(2-pyridyl) ketone (15.0 g, 81.4 mmol) wasweighed and introduced into the reactor. Hydrazine monohydrate (6.1 mL,185.7 mmol) was poured into the reaction mixture and the reactor closed.The reactor was mounted on a Parr heater unit and the reaction mixturestirred for 18 h at 150° C. at 28 bar. After 1 hour the temperature was150° C. and the pressure 5 bar. After 18 h heating and stirring thetemperature was 151° C. and the pressure inside the reactor 28 bar.After the reaction was complete, the cooled reactor was opened at airatmosphere and the yellowish liquid obtained neutralized with 1M HCl(aq.) and extracted with 3×50 mL chloroform. Organic phase was washedwith 3×30 mL of brine and dried over MgSO₄. Solvents were removed in avacuum and the crude product distilled in a vacuum to obtain a yellowliquid with b.p. 80-85° C./0.06 m bar. Yield: 9.8 g (72%). ¹H-NMR inCDCl₃; δ: 8.48 (m, 2H); 7.51 (m, 2H); 7.19 (t, 2H); 7.04 (m, 2H); 4.29(s, 2H). EIMS analysis showed parent ion of the title compound C₁₁H₁₀N₂corresponding to molecular weight M⁺=170.21 g mol⁻¹.

EXAMPLE 18

Synthesis of Dipyridin-methan-2-yl-potassium C₁₁H₉KN₂

Benzyl potassium 4.0 g (30.5 mmol) was added into a solution ofdipyridin-2-ylmethane 5.2 g (30.5 mmol) in 100 mL THF at −70° C. over 10minutes. The mixture was stirred at ambient temperature for 16 hoursafter which the bright yellow mixture was filtrated and washed with THF.Solvents were evaporated and the product washed with pentane andevaporated to yield a bright yellow solid which on the basis of the¹H-NMR spectrum in DMSO-d₆ was [DPM⁻K⁺] [THF]_(0.5). Yield 5.44 g(73.0%) based the THF complex (M_(w)=244.35 g mol−1). The productdecomposed during ETMS analysis. Elemental analysis calculated for[DPM^(−K) ^(+] [THF]) _(0.5): C 64.6%, H 4.8%, N 12.0%, K 21.9%. Found:C 63.9%, H 5.36%, N 11.46%, K 16.0%. NMR spectra were recorded at +22.7°C., +50° C. and at +70° C. in DMSO-d₆. The complex shows fluxionalbehaviour in NMR with increasing temperature which is caused by thetransition between the two resonance structures A and B. The peakscoalescence at +70° C. The singlet bridgehead proton is exchanged slowlywith the methyl deuterium of DMSO-d₆ which is seen as an appearingtriplet in ¹³C-NMR. ¹H-NMR in DMSO-d₆ at +70° C. δ: 8.20 and 6.25 (broadcoalesence peaks, 2H, from H_(a)++H_(a′)), 7.65 (d, 2H, fromH_(d)++H_(d′)), 6.78 (broad, 2H, from H_(b)++H_(b′)), 5.76 (broad, 2H,from H_(c)++H_(c′)), 4.62 (S, 1H, exchangeable proton H_(e)). ¹³C-NMR inDMSO-d₆ at δ: 160.2, 147.9, 147.8, 132.3, 131.2, 116.9, 114,3, 105.3,103.3, triplet 87.2 from exchanged CH_(e)++DMSO-d₆. ¹³C-CPMAS δ: 163,150, 138, 119, 109, 82.

EXAMPLE 19

Synthesis of triazabicyclodec-ene-yl-1-dimethylsilyl-dipyridin-methaneC₂₀H₂₇N₅Si

Dipyridin-methan-2-yl-potassium 2.62 g (12.6 mmol) dissolved in 100 mLTHF of was added into a solution oftriazabicyclodec-ene-yl-1-dimethylsilylchloride 2.90 g (12.6 mmol) in100 mL of THF over 40 minutes at −70° C. The mixture was stirred atambient temperature for 16 hours. Solvent was evaporated under vacuum,the product extracted in toluene, filtrated and washed with moretoluene. Solvent was removed under vacuum and the product grinded inglove box. The product was purified by washing with cold pentane.Pentane solubles were filtered off and the product evaporated undervacuum. Yield 3.7 g (80.0%) of yellow solid. EIMS analysis showed thedecomposition pattern of parent ion of the title compound C₂₀H₂₇N₅Sicorresponding to molecular weight M⁺=365.55 g mol⁻¹, fragmentation peaksat 335, 258, 196, 169, 138. ¹H-NMR in THF-d₈ δ: 8.45 (d, 2H), 7.45 (dd,2H), 7.44 (d, 2H) 6.99 (t, 2H). 4.92 (s, 1H), 3.06 (t, 4H), 2.86 (t,4H), 1.61 (q, 4H), 0.16 (s, 6H). Elemental analysis calculated: C 65.7%,H 7.44%, N 19.2%. found: C 63.8%, H 6.8%, N 16.6%.

EXAMPLE 20

Synthesis of Triazabicyclodec-ene-yl-1-dimethylsilyl dipyridylmethan-ylChromium Dichloride C₂₀H₂₈Cl₂CrN₅Si

1.9 mL methyl lithium (3.7 mmol, 1.94 M solution in diethyl ether) wasadded into a solution of triazabicyclodec-ene-yl-1-dimethylsilyldipyridylmethane 1.33 g (3.6 mmol) dissolved in 100 mL THF at −30° C.over 5 minutes. The mixture was stirred at ambient temperature for 2hours. CrCl₃(THF)₃ (3.6 mmol) was added at −30° C. over 30 minutes andthe solution stirred at ambient temperature over 16 hours. Solvents wereremoved under vacuum, the product extracted in toluene, filtered andevaporated. The product was purified by washing with colddichloromethane and pentane. Yield 0.2 g (25.5%) of dark brown tar. Theproduct decomposed during EIMS analysis. The product was paramagnetic,NMR identification could not be obtained.

EXAMPLE 21

Synthesis of Triazabicyclodec-ene-yl-1-dimethylsilyl dipyridylmethan-ylChromium Dichloride C₂₀H₂₈Cl₂TiN₅Si

0.8 mL methyl lithium (1.64 mmol, 1.94 M solution in diethyl ether) wasadded into a solution of triazabicyclodec-ene-yl-1-dimethylsilyldipyridylmethane 0.60 g (1.64 mmol) dissolved in 70 mL THF at −30° C.over 5 minutes. The mixture was stirred at ambient temperature for 16hours. TiCl₃(THF)₃ (1.64 mmol) was added at −70° C. over 20 minutes andthe solution stirred at ambient temperature over 3 hours. Solvents wereremoved under vacuum, the product extracted in toluene, filtered andevaporated. The product was purified by washing with colddichloromethane and pentane. Yield 0.5 g (64.9%) of dark brown tar. Theproduct decomposed during EIMS analysis. The product was paramagnetic,NMR identification could not be obtained.

EXAMPLE 22

Dimethylmethylene cyclopentadienyl triazabicyclodec-ene-yl-1 potassiumC₁₅H₂₂KN₃

Dimethylfulvene 1.8 mL (14.7 mmol) was added to(1.5.7-triaza[4.4.0]bicyclo-dec-5-enyl) potassium 2.6 g (14.7 mmol) inTHF at 0° C. over one hour. The mixture was stirred at ambienttemperature overnight, and the solvent removed under vacuum. The productwas washed with pentane and dried under vacuum to afford 3.2 g (79.05%)or light grey solid. ¹H-NMR in THF δ: 5.92 (dd, 2H), 5.65 (dd, 2H), 3.10(t, 4H), 3.04 (t, 4H), 3.81 (s, 6H), 3.61 (m, 4H). ¹³C-NMR in THF δ:151.0, 142.4, 121.9, 105.8, 102.9, 48.2, 41.8, 23.6, 22.2. MS analysisshowed the decomposition pattern of the parent title compound. No M⁺ wasdetected due to the decomposition of the sample during the analysis.Elemental analysis calculated C 63.56% H 7.82% N 14.82% K 13.79%, foundC 63.36% H 7.75% N 15.07% K 13.55%.

EXAMPLE 23

Dimethylmethylene cyclopentadienyl triazabicyclodec-ene-yl-1 chromiumdichloride C₁₅H₂₂Cl₂CrN₃.

Dimethylmethylene cyclopentadienyl triazabicyclodec-ene-yl-1potassiumCrCl₃(THF)₃ 3.4 g (9.08 mmol) in THF was added to a solutiuon oftriazabicyclodec-ene-yl-1-dimethyl-methylene potassium 2.6 g (9.08 mmol)in THF at −30° C. over a period of 30 minutes. The mixture was stirredovernight at ambient temperature. Solvent was removed under reducedpressure and the product extracted in toluene, filtrated and dried undervacuum. The filtrate was then extracted in dichloromethane, filtrated,and dried again under vacuum. The product was washed with pentane toafford pure dark blue microcrystalline solid 2.3 g (68.7%). EIMSanalysis showed the decomposition pattern of the title compound,M⁺=367.26 g mol⁻¹ peak was not detected due to decomposition duringanalysis. Elemental analysis calculated C 49.06% H 6.04% N 11.44% Cl19.31% Cr 14.16%, found C 47.81% H 6.06% N 13.05% Cl 18.80% Cr 13.60%.

Polymerization Examples

TABLE 1 Ethylene homopolymerization test results using homogeneouscatalysts Act. M_(w) × Cryst. m.p. Complex HOPO 10³ M_(w)/M_(n) % ° C.Al/M Example 6 2778 n.d. n.d. 53.6 134.3 757Me₂Si(Me₂Cp-OSiMe₂—tBu)(TAB)CrCl₂ Example 8 395 977 30.2 57.1 135.1 778Me₂Si(Cp-OSi—iPr₃)(TAB)CrCl₂ Example 13 1048 412 27.8 66.7 133.2 1000Ph₂Si(Me₄Cp)(TAB)CrCl₂ Example 10 50 272 6.6 58.9 134.2 1000Me₂Si(Flu)(TAB)CrCl₂ ¹Al/M ratio 700-1000, MAO, temp +60° C., C₂ = 10bar. n.d. = not determined (too high M_(w) for GPC measurement device).Activity in [kg PE/g met, h⁻¹]

TABLE 2 Ethylene homopolymerization using homogeneous catalysts andhydrogen Act. M_(w) × Cryst. m.p. Complex HOPO/H₂ 10³ M_(w)/M_(n) % ° C.Al/M Example 6 1902¹   198 7.4 71.1 132.5 1000Me₂Si(Me₂Cp-OSiMe₂—tBu)(TAB)CrCl₂ Example 13 2628.1 — — — — —Ph₂Si(Me₄Cp)(TAB)CrCl₂ Example 8 486  192 8.1 67.3 135.7  763Me₂Si(Cp-OSi—iPr₃)(TAB)CrCl₂ ¹Amount of hydrogen fed to the 2 L reactorwas 0.6 bar/677 mL ²Amount of hydrogen fed to the 2 L reactor was 0.3bar/677 mL. n.d. = not determined (too high M_(w) for GPC measurementdevice). Activity in [kg PE/g met. h⁻¹]. Temp. +60° C.

TABLE 3 Copolymerization of ethylene and 1-hexene using homogeneouscatalysts Act. Complex COPO Example 13 2713.5 Ph₂Si(Me₄Cp) (TAB) CrCl₂Example 23 91.62 Me₂C(Cp) (TAB) CrCl₂ Activity in [kg PE/g met. h⁻¹]

TABLE 4 Polymer double bond analysis results of the ethylenehomopolymers^(#) Complex t-vinylene vinyl vinylidene Example 6 0.11 0.090.03 Me₂Si (Me₂Cp-OSiMe₂—tBu) (TAB) CrCl₂ Example 8 n.d. n.d. n.d. Me₂Si(Cp-OSi—iPr₃) (TAB) CrCl₂ Example 13 0.21 0.71 0.12 Ph₂Si (Me₄Cp) (TAB)CrCl₂ Example 10 0   0.18 0.05 Me₂Si (Flu) (TAB) CrCl₂ ^(#)Unit isdouble bonds per 1000 carbon atoms (C═C/1000C).

TABLE 5 Propylene polymerisations. Al/Cr ratio 1000, polymerisation time90 minutes. 5 bar propylene pressure (60° C.). Cocatalyst MAO & TIBA(tetraisobutylalumoxane) 150 μL, 1100 g propylene. Complex Yield ofPolymer Notes Example 6 0.7 g Example 6 1.4   6 g Ethylene added

TABLE 6 Analysis results of the polymers DSC, MN MW MW/ MZ T- Code RunType DSC (%) TCR1 (° C.) TM1 (° C.) (g/mol) (g/mol) MN (g/mol) MFR21VINYL VINYL VINYLIDEN 8 HOPO60 57.1 115.9 135.1 32300 977000 30.26302000 0.03 8 HOPO80 64 116.2 129.9 not done 0.16 1.46 0.6 8 HOPO/H26067.3 116.3 135.7 23600 192000 8.1 1392000 14.5 0 0.27 0.1 6 HOPO60 53.6115.9 134.3 0.008 0.11 0.09 0.0 6 HOPO80 72.3 118.2 131.3 28.4 0.84 0.680.2 6 HOPO/H260 71.1 119 132.5 26900 198000 7.4 3553000 42.5 0.06 0.090.0 Heterogeneous polymerisation test result of compound 20 using silicaActivity of cat Activity of metal Flowmeter DSC Pol type (KgPol/g cat h)KgPol/g met h) Al/Me C2 (g) Temperature (° C.) CR1 (%) TCR1 (° C.) TM1(° C.) HDPE 0.01 4.6 200 28 60 49.1 119.9 113.4 HDPE 0.00 4.3 200 24 8051.3 120 132.5 GPC-Normal MFR FTIR, (C═C/1000C) MN1 MW1 MW1/MN1 MZ1 21.6KG T-VINYLENE VINYL VINYLIDENE 204600 1899000  9.3 6079000 not done X XX  19000 1742000 91.7 9030000 not done X X X

What is claimed is:
 1. A compound of formula (I)

wherein LIG represents an η⁵-ligand substituted by a group R₁ and agroup (R″)_(m); X represents a 1 to 3 atom bridge; Y represents anitrogen or phosphorus atom; Z represents a carbon, silicon, nitrogen orphosphorus atom; the ring denoted by A₁ is an optionally substituted,optionally saturated or unsaturated 5 to 12 membered heterocyclic ring;the ring denoted by A₂ is an optionally substituted, unsaturated 5 to 12membered heterocyclic ring; R₁ represents hydrogen, R″ or a groupOSiR′₃; each R′, which may be the same or different is a R⁺, OR⁺, SR⁺,NR⁺ ₂ or PR⁺ ₂ group where each R⁺ is a C₁₋₁₆ hydrocarbyl group, atri-C₁₋₈hydrocarbylsilyl group or a tri-C₁₋₈hydrocarbylsiloxy group;each R″, which may be the same or different is a ring substituent whichdoes not form a σ-bond to a metal η-bonded by the bicyclic ring; and mis zero or an integer between 1 and
 3. 2. A compound as claimed in claim1 wherein Z represents a nitrogen atom.
 3. A compound as claimed inclaim 1 or 2 wherein Y represents a nitrogen atom.
 4. A compound asclaimed in claim 1 wherein A₁ and A₂ are five or six-membered rings. 5.A compound as claimed in claim 1 or 4 wherein A₁ and A₂ areunsubstituted and comprise only 1 double bond.
 6. A compound as claimedin claim 1 wherein A₁ and A₂ represent


7. A compound as claimed in claim 1 wherein LIG comprises adipyridymethanyl, cyclopentadienyl, fluorenyl or indenyl ligand.
 8. Acompound as claimed in claim 1 wherein R″ represents hydrogen, R⁺, OR⁺,SR⁺, NR⁺ ₂ or PR⁺ ₂ group where each R⁺ is a C₁₋₁₆ hydrocarbyl group, atri-C₁₋₈ hydrocarbylsilyl group or a tri-C1.8hydrocarbylsiloxy group. 9.A compound as claimed in claim 7 or 8 wherein LIG representscyclopentadienyl and R₁ represents OSiR′₃ each R′ being a C₁₋₁₂hydrocarbyl group.
 10. A compound as claimed in claim 9 wherein R″represents C₁₋₆ alkyl.
 11. A compound as claimed in claim 1 wherein LIGrepresents


12. A compound as claimed in claim 1 wherein m is 3, LIG is acyclopentadienyl and R″ is methyl.
 13. A compound as claimed in claim 1wherein X is a one atom bridge comprising Si or a one atom bridgecomprising a carbon atom.
 14. A compound as claimed in claim 1 whereinLIG represents fluorenyl, indenyl or dipyridymethanyl and R′ and R″represent hydrogen.
 15. A compound as claimed in claim 1 of formula


16. A procatalyst comprising a compound of formula (I) as claimed inclaim 1 coordinated to a metal ion of group 3 to 7, the Y atom not beingcoordinated to the metal.
 17. A procatalyst as claimed in claim 16wherein said metal ion is an ion of Cr or Ti.
 18. A procatalyst asclaimed in claim 16 or 17 wherein said metal is additionally coordinatedto a halogen σ-ligand.
 19. A procatalyst as claimed in claim 16 or 17wherein at least one of the atoms N or Z or the double bond of thebicyclic ring is coordinated to the metal ion.
 20. A procatalyst asclaimed in claim 19 wherein the group LIG and the atom N are coordinatedto the metal ion.
 21. An olefin polymerisation catalyst systemcomprising or produced by reaction of (1) a procatalyst as claimed inclaim 16 and (2) a cocatalyst.
 22. A process for olefin polymerisationcomprising polymerising an olefin in the presence of a catalyst systemas described in claim
 21. 23. A process for the preparation of aprocatalyst, said process comprising metallating with a group 3 to 7transition metal a compound of formula (I)

wherein LIG represents an η⁵-ligand substituted by a group R₁ and agroup (R″)_(m); X represents a 1 to 3 atom bridge; Y represents anitrogen or phosphorus atom; Z represents a carbon, silicon, nitrogen orphosphorus atom; the ring denoted by A₁ is an optionally substituted,optionally saturated or unsaturated 5 to 12 membered heterocyclic ring;the ring denoted by A₂ is an optionally substituted, unsaturated 5 to 12membered heterocyclic ring; R₁ represents hydrogen, R″ or a groupOSiR′₃; each R, which may be the same or different is a R⁺, OR⁺, SR⁺,NR⁺ ₂ or Pr⁺ ₂ group where each R⁺ is a C₁₋₁₆ hydrocarbyl group, atri-C₁₋₈hydrocarbylsilyl group or a tri-C₁₋₈hydrocarbylsiloxy group;each R″, which may be the same or different is a ring substituent whichdoes not form a σ-bond to a metal η-bonded by the bicyclic ring; and mis zero or an integer between 1 and 3.